Taiwan opened ports after the second Opium War. This paper investigates whether this opening event stimulated Taiwan's sugar export, and we find opening trade with foreign direct investment banned promoted sugar exports in a limited manner. Though Taiwan's sugar exports expanded greatly when ports were opened, this should be largely attributed to the ending of the Taiping Rebellion which reset Taiwan's trading pattern. Japan's opening of its ports did boost Taiwan's sugar trade, but Taiwan's sugar, which was produced in a backward manner, had difficulty competing with other Asian sugar produced by modern technology. When the sugar crisis took place in 1884, Java and the Philippines started to shift their sugar markets from the West to Asia. They won a large market share in China and Japan and depressed Taiwan's sugar industry.